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Research Notes

Removing endocrine-disrupting compounds from the water stream

Adding one more step to water treatment can help
remove endocrine-disrupting compounds. University of Texas at El Paso
researchers are developing a process to remove these compounds from reclaimed
and drinking water, according to a university news release.

The compounds, found in such household and industrial
products as detergents and pesticides, can disrupt the hormonal balance in
humans and wildlife. After humans use or consume products containing
endocrine-disrupting compounds, the chemicals end up at water resource recovery
facilities, which cannot entirely remove them from the water, the news release
says.

Wen-Yee Lee, associate professor of chemistry at the
university and the study’s principal investigator, sampled local wastewater
before and after treatment to find that much of the compounds escape treatment
and re-enter the environment through reclaimed and drinking water, the news
release says.

To remove the compounds, Lee’s research team
constructed additional disinfection processes using ultraviolet rays and
chlorination to help achieve removal, the news release says.

The team continues to refine this process, aiming for
complete removal of the compounds, and plans to expand the study to six
municipal water resource recovery facilities in El Paso and Socorro, N.M. While
these compounds currently are not regulated, the team hopes their findings will
provide an effective treatment process to respond to any future potential
regulations, the news release says.

Nitrogen moves slowly through groundwater

Nitrogen does not move through groundwater channels in
a matter of days, months, or even years; it can take decades, according to U.S.
Geological Survey (USGS) hydrologic researchers.

The researchers examined surface and groundwater at
seven sites across the United States and determined that nitrate in streams was
derived from groundwater, according to a USGS news release. This occurred
mainly in groundwater-dominated watersheds where rivers and streams are fed
predominantly by groundwater held in underground aquifers.

To determine the time nitrate takes to reach a stream
from groundwater, the researchers conducted an age-dating tracer study in the
Tomorrow River in central Wisconsin.

“Findings indicated that decades-old nitrate-laden
water currently was discharging to this stream,” the news release says. The
researchers determined that base-flow nitrate concentrations in the stream may
be sustained for decades regardless of current and future practices.

The study was conducted because water quality experts
recently have been documenting that nitrate trends in streams and rivers do not
meet expectations based on reduced regional use of nitrogen-based fertilizer.
Long travel times of groundwater discharge have been suggested as the factor
likely responsible for these observations, the news release says.

The delay means that changes in the use of
nitrogen-based fertilizer, a typical source for nitrate in waterways, may take
decades to be fully observed in streams, the research indicates. And because
waterways obtain more water from groundwater during low flows, nitrate
concentrations increase during low and moderate flows in large rivers, the news
release says.

A report on the study results, “Vulnerability of
Streams to Legacy Nitrate Sources,” was published in the journal Environmental
Science and Technology.

Gasoline-denatured ethanol shows promise for
denitrification

During biological nutrient removal, water resource
recovery facilities add carbon to post-anoxic denitrification process. Using
three lab-scale sequencing batch reactors, researchers evaluated the
performance of three carbon sources — methanol, ethanol, and gasoline-denatured
ethanol. Results of the study are published in the June issue of Water
Environment Research.

After examining the treatment efficiency and cost of
each carbon source, the researchers determined that the use of
gasoline-denatured ethanol was “very promising,” the article says.

While this carbon source costs more than methanol, it
had the benefits of high denitrification rates, a higher observed growth yield,
commercial availability, ready biodegradability, short adaption periods, and no
federal alcoholic beverage tax. “Utilities will have to decide if it is worth
paying a little extra to take advantage of its benefits,” the report says.

To enhance the potential use of denatured ethanol in
denitrification, the researchers note a need to examine the efficiency of
denatured ethanol at cold temperatures through long-term operations on a larger
scale, to determine the possibility of using substrates interchangeably, and to
determine a maximum specific growth rate and half-saturation constant, the
report says.

The report, “Evaluation of
Gasoline-Denatured Ethanol as a Carbon Source for Denitrification,” is
available as an open-access document and can be downloaded free at http://goo.gl/yYAEH.

Water Environment Research allows open access to one article per issue on a range of important technical topics such as nutrient removal, stormwater, and biosolids recycling.